There is always that fine line between econ anf pep too. I have a 2.4 but coming from a truck getting 24.5 in city driving by being a lttle careful is great yet I have that 179HP if needed. I have used both prem. and reg. and see no difference in mpg and just a very slight bit of power and that is questionalble.Running it normal, not being careful pulling away from lights etc. driving like the gas is cheap (it is) gives me about 22+

The 2.2 develops 149HP vs 170 something for the 2.4. Premium fuel is suggested for the 2.4, 87 octane for the 2.2. I have a 2.2 with a five speed, and have never felt it was underpowered, but perhaps having a manual transmission helps more than I think it does. I would certainly buy the same setup again if I were in the market today.

This is a bit off topic, but our car(Homer- the wife hates the name!) has the 2.4 and gives lots of power for its size. In Canada we have a 10% ethanol blend and a chain called Mohawk/ Husky that sells 90 octane for the same price as 87. In my Scout, the performance difference is very noticeable. I try to use the 90 blend whenever I go on long distances with heavy grades. Even around town it helps on hills leading home, however, not enough to offset the discounts I get at the local Superstore Gas Bar in the Scout that is- the HHR gets the best at all times, unless there is no option when traveling; then you must take what you can get.

I am driving a 2009 HHR now as a rental while my car is in the shop for warranty work and it has the 2.2 engine. With 149HP, this must be the same engine Saturn uses as the HHR drives a lot like our old VUE did.

Since we got our car 4 months ago, I can promise you this ....you WILL motice a harder feel and the knocking mentioned if you do not put premium fuel in the 2.4. as it details in the manual. I did not realize this when I first bought it and was complaining ab my mpg. After i fixed the error, my mpg is now where it supposed to be , even better . So you are not really paying more if your gas milage increases. If you do the math, it comes out right. i dont have any figures in front of me and I appologize for that,.but im on the rn this morning! But all in all, using the premium has not been a problem or cost us any more.

The diff between the 2 are Hp ratings and the 2.4 Does reqiure Premium Fuel . Look in your owners manual, we found out the hard way . The engine started to ping and act like it was missing so I called the Dealer and asked the service manger about this and was asked what grade of gas we were using . We started putting Super iin it and the problem went away.

My HHR is a 2010 LT with the 2.4 L engine and I never filled it with premium gasoline always regular but "Top Tier Gasoline" if possible. It has 26,000 miles on it, went on a cross country trip (2 adults) with cargo area fully loaded (back seat down), got 32.2779 m/p/g max. (prairies @ 70-75 m/p/h.) and 27.9989 m/p/g min. (rockies @ 65-70 m/p/h. ). Never heard a pinking sound what so ever. Premium gas is "Recommended" but not "Required" (owner's manual). Big difference between those 2 words.

I didn't realize about the premium gasoline until I read these threads here. As I mentioned before, my best friend used to be an engineer at Exxon/Mobil and he told me never to use the higher octane gas until your car "needed" it because once you start using it, you will have problems if you ever go back to 87. After reading these threads on fuel economy, I noticed my car was missing a little when I accelerated going up hills. (Never had any knocking or any other acceleration issues. Just on hills.) I asked him about it, and he told me to check my manual and if the manufacturer "recommended" higher octane gas to put what it said in there and never change back. I put 93 octane in on my last tank, and I am already noticing an increase in MPG of a few miles, not to mention no more acceleration issues.

Also, to touch on what the last poster said, my co-worker's husband is a GM master mechanic at a Chevy dealership, and he said it matters less what octane of gas you put in and more of where you are getting your gas. He said it is more important to get high quality gas and avoid the cheaper gas stations.

I never bought a Cavalier with the 2.4L engine, but I can't imagine having an HHR with a 2.2L. It just seems like with the greater curb weight it makes sense to have a little bigger engine for more pick-up.

Pretty much the same m/p/g here with my 2010 2.4L with 25,000 miles on. To bad the last production line are the 2011 models. Probably it was to good G.M. had to stop building them? Looking towards the new Chevrolet Trax or the Sonic "Hatchback" but only in 2015/16 otherwise it would have been another HHR.